1. Field of the Invention
This invention relates to a vehicle seat incorporating an airbag (i.e., side airbag) at one side of the seat back.
2. Description of the Related Art
The vehicle seat comprises a seat cushion and a seat back coupled at lower edge to the rear edge of the seat cushion. In most cases, the seat back can be inclined by means of a reclining device.
A spring assembly has, for example, many S springs used as shock absorbing members, which are stretched in a frame (i.e., seat back frame). The frame is covered with a pad (i.e., seat pad) made of plastic foam, thereby forming a seat back unit. The seat back unit is covered with a trim cover (surface sheet), whereby a seat back is formed.
Vehicle seats incorporating a side airbag are widely known. If another vehicle hits the vehicle at side, the airbag provided at the vehicle wall side of the vehicle seat will inflate and develop, reducing the impact to the occupant and thus protecting the occupant.
Of a vehicle seat of this type, the two trim cover strips (i.e., forward and rearward strips) of the trim cover are sewn at the front parts of the sides of the seat back. At the back of the sewn parts of the trim cover, the pad of the seat back has a space (a side space) in which an airbag (side airbag) is arranged.
The airbag (side airbag) incorporates a micro gas generator called inflator, is folded in front of the inflator, and is contained in a substantially rectangular case. The airbag contained in the case is secured to one side frame provided at the vehicle wall side of the seat back frame. The airbag is arranged and incorporated in the space made in the pad (i.e., space in the side part of the seat back). The seat has an impact sensor. The impact sensor detects an impact at a side of the vehicle if another vehicle hits the vehicle at that side. Then, the inflator is activated, generating gas (high-pressure gas). The gas gushes in the airbag and inflates the airbag. So inflated, the airbag first breaks the pad and then tear up the sewn part of the trim cover on the vehicle wall side. The airbag then inflates at the vehicle wall side and to the fore-side of the occupant. As a result, the airbag isolates the occupant from the vehicle wall. The pad that is adjacent to the sewn parts of the trim cover is made thin in most cases, and can easily provide a passage (development passage) through which the airbag may reach the sewn parts of the trim cover.
In most cases, the seat back frame is composed of upper and lower frames and left and right side frames, all made of steel plates or steel pipes, and is a rectangular frame as seen in the plan view. The left and right side frames extend in forward direction.
As seen also from FIG. 3 of JP 2009-035089A, the airbag is provided at the vehicle wall side and secured to the outside of the seat back. More precisely, the airbag is secured to the outside of the side frame on the vehicle wall side of the seat back frame, and is incorporated in the side space of the seat back. That is, the airbag is fastened to the outside of the side frame on the vehicle wall side, and the side frame is located inside the airbag. Located inside the airbag, the side frame controls (or interrupts) the airbag, preventing the airbag from developing toward the occupant. Inevitably, the airbag develops in a specific passage extending toward the sewn parts of the trim cover, which exist at the front side parts of the seat back.
Patent Literature: Japanese Patent unexamined Publication JP 2009-035089A
As descried above, in the vehicle seat incorporating a side airbag, the side airbag is provided outside of the side frame on the vehicle wall side. The airbag is controlled (or interrupted) by side frame and cannot develop toward the occupant of the vehicle seat. The airbag therefore develops in a specific passage that extends, on the vehicle wall side, toward the sewn parts of the trim cover. However, a space for the airbag is provided in the pad of the seat back, and the airbag is arranged in the space and covered with the trim cover. Further, the trim cover covers the pad of the vehicle seat. The side of the seat back inevitably bulges outward at the vehicle wall side where the airbag is located. Hence, the vehicle wall side part of the seat back, where the airbag is provided, differs in shape from the vehicle inner part of the seat back, where no airbag is provided. Consequently, the left and right sides of the seat back will differ in design.
The object of this invention is to provide a vehicle seat incorporating a side airbag at one side of the seat back, without making any design difference between the left and right sides of the seat back, and in which the airbag is prevented from developing toward the occupant of the vehicle seat, and develops in a specific passage extending on the vehicle wall side.